With road building projects, such as building a new road or renewing damaged road surfaces, the quality of the newly applied road building material is to be documented by the executing companies using check tests. Measuring the temperature of the asphalt layer directly after being mounted by the road finishing machine is among these tests. The temperature of the newly applied road building material is measured over the entire placement width directly behind the asphalt plank of the road finishing machine.
A roadway temperature monitoring system comprising a temperature sensor is known from WO 00/70150 A1. The temperature sensor here may either by a thermal-imaging camera, a thermal scanner or a thermal-imaging camera operating in a “line scan” mode. The temperature sensor is arranged at the back end of a road finishing machine such that the entire width of the newly applied asphalt layer is scanned. The captured temperature values may be displayed graphically on a display device.
Disadvantageous with such a temperature sensor is the fact that a thermal-imaging camera or thermal scanner is usually very expensive to buy. In particular, for smaller building companies such an investment usually cannot be realized due to the high costs. Furthermore, it is disadvantageous that the detection or opening angles of a thermal-imaging camera or a thermal scanner are highly limited such that, with mounting, or placement, widths in a range of 8 to 12 meters, for example, a correspondingly adapted objective lens has to be applied at the thermal-imaging camera in order to be able to detect the entire placement width of the newly applied road building material. This, in turn, increases the cost of such a temperature sensor further. Alternatively, both the thermal-imaging camera and the thermal scanner would have to be applied in a correspondingly elevated position at the road finishing machine, i.e. a lot more than four meters above the surface of the newly applied road building material, in order to be able to detect the entire placement width of the newly applied road building material. However, this is of particular disadvantage when passing below bridges.
However, when mounting the thermal-imaging camera or thermal scanner at the road finishing machine in an advantageous area of 3 to 4 meters above the surface of the newly applied road construction material, due to the limited detection or opening angle, a correspondingly flat assembly angle relative to the surface of the newly applied road building material may be employed (cf. FIG. 2, assembly angle γF may be large) in order for the entire placement width of the newly applied road building material to be detected. However, the temperature of the newly applied road building material over the entire placement width is not measured directly behind the asphalt plank of the road finishing machine but in a correspondingly large distance to the back edge of the asphalt plank. Consequently, the temperature values measured no longer correspond to the actual values in the area directly behind the asphalt plank.
A device, as described above, for measuring the temperature of the surface of hot asphalt, including an infrared temperature measuring head moving transverse to the direction of travel, a motor for moving this sensor and a controller, is known already from DE 20 2009 016 129 U1.
Based on this device, calculating the placement width of the newly applied asphalt layer is known from DE 20 2013 001 597 U1. Same is calculated using the height of the measuring head above the asphalt layer, which is determined using a distance sensor, and the angle values where the measuring head changes its direction of movement.
When capturing the temperature measuring values by means of the known device, however, the result is not a steady measuring point pattern. As the assembly position and/or the assembly angles of the device change, so does the distance between the measuring points on the surface of the newly applied road building material. In addition, the distance between the measuring points in the direction of travel of the construction machine changes with a changing speed of travel of the construction machine. If same moves faster, the distance between the measuring points in the direction of travel will become larger.
Post-published DE 10 2014 222 693 A1 describes a device for determining the temperature of a road building material applied at a placement width by a construction machine, said device being arranged on the construction machine in the area within the placement width and comprising an infrared temperature measuring head, a motor and a controller. The infrared temperature measuring head is arranged to be twistable by the motor in a direction transverse to the direction of travel of the construction machine, and is effective to capture, during a rotational movement temperature measuring values of the surface of the road building material at at least two measuring points spaced apart from one another. The controller is effective to control the motor, on the basis of the mounting position of the device on the construction machine, such that the distance between the measuring points on the surface to be measured remains the same.
Temperature measurements performed by means of a temperature scanner known from conventional technology are less precise in the area of the asphalt edges, or roadway edges, e.g. to the left and to the right and/or in the area of the end of the plank or of the outer edge of the plank, than they are within the central area, e.g. in the area of the center of the plank. In the temperature scanners known from conventional technology, the asphalt surface temperature is determined by means of a constant dwell time for measurement in that the scanner is stopped at every measuring point. The dwell time is approx. 10 ms or 20 ms, for example. As is described in DE 10 2014 222 693 A1, for example, the time constant is adjustable.